diff --git a/cryptest.nmake b/cryptest.nmake
index 1c547ed3..f759b650 100644
--- a/cryptest.nmake
+++ b/cryptest.nmake
@@ -154,7 +154,7 @@ LDLIBS =
 # Debug build.
 # CXXFLAGS = $(CXXFLAGS) /DDEBUG /D_DEBUG /Oi /Oy- /Od /MTd
 # Release build. Add /OPT:REF to linker
-CXXFLAGS = $(CXXFLAGS) /DNDEBUG /D_NDEBUG /Oi /Oy /O2 /MT
+CXXFLAGS = $(CXXFLAGS) /DNDEBUG /D_NDEBUG /Oi /Oy /O2 /MT /openmp
 # Linker flags.
 LDFLAGS = $(LDFLAGS) /OPT:REF
 
diff --git a/scrypt.cpp b/scrypt.cpp
index 27e604ee..667d7cb3 100644
--- a/scrypt.cpp
+++ b/scrypt.cpp
@@ -14,6 +14,8 @@
 #include "sha.h"
 
 #include <sstream>
+#include <limits>
+
 #ifdef _OPENMP
 # include <omp.h>
 #endif
@@ -189,7 +191,7 @@ void Scrypt::ValidateParameters(size_t derivedLen, word64 cost, word64 blockSize
     {
         std::ostringstream oss;
         oss << " parallelization " << parallelization << " is larger than ";
-        oss << numeric_limits<int>::max();
+        oss << std::numeric_limits<int>::max();
         throw InvalidArgument("Scrypt: " + oss.str());
     }